Do I have to talk to the judge or jury?

No.

The defendant has a Constitutional right to remain silent. Whether to put the defendant on the witness stand is a decision the defendant and the defense attorney must make. Defense attorneys agree that it is sometimes better to keep the defendant off the witness stand, except in special cases.

Once the defendant testifies, the defendant opens him/herself up to cross-examination by the prosecution. Because of this Constitutional right, the judge will instruct the jury that the defendant's failure to testify must not be considered in any way a sign that the defendant is guilty. Of course, if a defendant is entering a plea or accepting a plea bargain, the defendant must answer the judge's basic questions with regard to the defendant's understanding of these actions.